Rails 4强参数和嵌套形式

Question

我正在构建一个简单的应用程序（Ruby 2.0.0和Rails 4），其中用户可以创建项目并为每个项目创建多个屏幕。当创建一个屏幕时，用户可以上传截图，这个截图是指它自己的模型（我这样做是为了处理同一个屏幕的多个版本）。

创建屏幕时，由于权限问题，屏幕截图似乎不会创建。这里的服务器日志：

Processing by ScreensController#create as HTML 
Parameters: {"utf8"=>"✓", "authenticity_token"=>"kezaGADsaLmY/+zozgbjEe5UfdeqRPg58FCf1qzfHxY=", "screen"=>{"project_id"=>"24", "name"=>"Billing", "description"=>"This is the page where a user will enter their credit card information", "screenshot"=>{"image"=># <ActionDispatch::Http::UploadedFile:0x007fcdce25b2c0 @tempfile=#<Tempfile:/var/folders/pv/srwrv0qj35b0hsxkt42l_z500000gn/T/RackMultipart20131007-91790-tewse9>, @original_filename="fb-banner.png", @content_type="image/png", @headers="Content-Disposition: form-data; name=\"screen[screenshot][image]\"; filename=\"fb-banner.png\"\r\nContent-Type: image/png\r\n">}}, "commit"=>"Create Screen"} 
Unpermitted parameters: screenshot 

这是我的模型：

屏幕

class Screen < ActiveRecord::Base 

    belongs_to :project 
    has_many :screenshots 

    validates :name, presence: true 

    accepts_nested_attributes_for :screenshots 

end 

截图

class Screenshot < ActiveRecord::Base 

    belongs_to :screen 

end 

这是我screens_controller：

class ScreensController < ApplicationController 
    before_action :set_screen, only: [:show, :edit, :update, :destroy] 


    def index 
    @screens = Screen.all 
    end 


    def show 
    end 


    def new 
    @screen = Screen.new(:project_id => params[:project_id]) 
    @screen.screenshot.build 
    end 


    def edit 
    end 


    def create 
    @screen = Screen.create(screen_params) 
    if @screen.save 
     flash[:notice] = "A new screen has been added to this project" 
     redirect_to [@screen.project] 
    else 
     render :action => 'new' 
    end 
    end 


    def update 
    @screen = Screen.find(params[:id]) 
    if @screen.update_attributes(screen_params) 
     flash[:notice] = "The screen has been successfully updated" 
     redirect_to [@screen.project] 
    else 
     render :action => 'edit' 
    end 
    end 

    def destroy 
    @screen = Screen.find(params[:id]) 
    @screen.destroy 
    flash[:notice] = "Successfully destroyed screen" 
    redirect_to [@screen.project] 
    end 

    private 
    def set_screen 
     @screen = Screen.find(params[:id]) 
    end 

    def screen_params 
     params.require(:screen).permit(:project_id, :name, :description, screenshot_attributes: [ :id, :screen_id, :image, :version ]) 
    end 
end 

最后是这样的形式：

<%= form_for @screen, :html => { :multipart => true } do |f| %> 
    <% if @screen.errors.any? %> 
    <div id="error_explanation"> 
     <h2><%= pluralize(@screen.errors.count, "error") %> prohibited this screen from being saved:</h2> 

     <ul> 
     <% @screen.errors.full_messages.each do |msg| %> 
     <li><%= msg %></li> 
     <% end %> 
     </ul> 
    </div> 
    <% end %> 

    <div class="field"> 
    <%= f.hidden_field :project_id %> 
    </div> 
    <div class="field"> 
    <%= f.label :name %><br> 
    <%= f.text_field :name %> 
    </div> 
    <div class="field"> 
    <%= f.label :description %><br> 
    <%= f.text_field :description %> 
    </div> 

    <%= f.fields_for :screenshot do |s| %> 
    <%= s.hidden_field :screen_id, :value => @screen.id %> 
    <%= s.hidden_field :version, :value => "1" %> 
    <%= s.label :image %><br> 
    <%= s.file_field :image %> 
    <% end %> 

    <div class="actions"> 
    <%= f.submit %> 
    </div> 
<% end %> 

我希望这是足以帮助我发现这个问题。在编程方面，我是一个新手，所以任何帮助都是值得欢迎的。

Answer 1

最近，我通过类似的工作，这是什么似乎工作...

您fields_for改为复数：

<%= f.fields_for :screenshots do |s| %> 

而且也使您的PARAMS

def screen_params 
    params.require(:screen).permit(:project_id, :name, :description, screenshots_attributes: [ :id, :screen_id, :image, :version ]) 
end 

此外，您需要更新您的new动作以制作复数截图，如下所示：

def new 
    @screen = Screen.new(:project_id => params[:project_id]) 
    @screen.screenshots.build 
end